1. Field of the Invention
The present invention relates to a communication apparatus.
2. Description of the Related Art
A caller ID service, which is also referred to as “a number display service”, has been already known. In the caller ID service, firstly, an exchanger performs polarity reversal of a communication line through which the exchanger and a communication apparatus on a receiving side are coupled to each other. Then, the exchanger transmits a terminal activation signal (CAR signal) to the communication apparatus on a receiving side. After detecting the CAR signal, the communication apparatus on the receiving side transmits a primary response signal to the exchanger. Subsequently, after receiving the primary response signal from the communication apparatus on the receiving side, the exchanger transmits a caller telephone number such as a telephone number of a caller. In the communication apparatus on the receiving side, after a reception completion signal representing that the caller telephone number has been received is transmitted to the exchanger, a calling signal (IR) is received from the exchanger, then the caller telephone number that has been received is displayed and a communication with a caller apparatus is started.
Specifically, in the communication apparatus on the receiving side, when the terminal activation signal (CAR) is received after the polarity reversal, the line is closed to receive the caller telephone number, and then the line is opened to stand by for the calling signal (IR). After that, when the calling signal (IR) is received, the caller telephone number that has been received is displayed.
In the communication apparatus on the receiving side, the communication with the caller apparatus may be disconnected during the period, that is, from the time when the caller telephone number is received to the time when the calling signal (IR) is received. If another calling signal (IR) is received from a different caller apparatus during the period, a caller telephone number of the caller apparatus different from the caller apparatus with which communication is established may be displayed.
In order to suppress such an error output, a technology is disclosed in Japanese Patent No. 3506811, in which when polarity reversal of the line is detected and then another polarity reversal is detected while a calling sound is output to a telephone set of a receiving side, the output of the calling sound is discontinued.
However, in the related art, although the output of the calling sound can be disconnected, the error display of a caller telephone number due to disconnection of the communication with the caller cannot be suppressed.
Therefore, there is a need for a communication apparatus capable of suppressing an error display of a caller telephone number.